The Colorado National Monument is west of Grand Junction and south of Interstate 70. According to the Guide To The Geology of Colorado written by Andrew M. Taylor,The plateau was uplifted during the Laramide Orogeny of Late Cretaceous and Early Tertiary, creating a large easily visible monoclinical fold in the rocks on the northeastern side. The Monument is an area of beautiful scenery compsed of impressive steep-walled canyons eroded into the plateau. these canyons are the roason for the designation of the area as a Monument.
Rocks exposed in the canyon walls are of Triassic age. Jurassic and Cretaceous rocks are present farther back from the canyons. these are sedimentary rocks composed of shales and sandstones. At the base of the canyon walls, Triassic rocks overlie Precambrian metamorphic gneisses and schists. This is a major unconfomity and was created by erosion of the ancestral Uncompaghre Uplift of Pennsylvanian age.
This is the unconformity of the layers
The ancestral mountains in this area were not completely eroded away, and covered by younger sediments, until the Triassic Period. The Triassic Chinle Formation overlies the Precambrian, and the Triassic Wingate Sandstone forms the cliffs above. Erosion of the sandstones within the canyons has produced scenic pinnacles.
Example of weathering formations
Receding back from the cliffs are the Triassic Kayenta Formation, the Jurassic Entrada and Morrison formations and the Cretaceous Burro Cnayon and Dakota formations. Remnants of Cretaceous Mancos Shale cap the centers of the plateaus.
No Thoroughfare Canyon at the Colorado National Monument has canyon walls made up of Chinle and Wingate formations and there are some tops of Kayenta and Entrada Sandstones. The trail is on Precambrian rocks.
Bibliography
Taylor, Andrew M. "Colorado National Monument." Guide to the Geology of Colorado. Golden, CO: Cataract Lode Mining, 1999. Print.
No Thoroughfare Canyon Trail
No Thoroughfare Canyon Google Earth Tour.kmz
The Colorado National Monument is west of Grand Junction and south of Interstate 70. According to the Guide To The Geology of Colorado written by Andrew M. Taylor,The plateau was uplifted during the Laramide Orogeny of Late Cretaceous and Early Tertiary, creating a large easily visible monoclinical fold in the rocks on the northeastern side. The Monument is an area of beautiful scenery compsed of impressive steep-walled canyons eroded into the plateau. these canyons are the roason for the designation of the area as a Monument.
Rocks exposed in the canyon walls are of Triassic age. Jurassic and Cretaceous rocks are present farther back from the canyons. these are sedimentary rocks composed of shales and sandstones. At the base of the canyon walls, Triassic rocks overlie Precambrian metamorphic gneisses and schists. This is a major unconfomity and was created by erosion of the ancestral Uncompaghre Uplift of Pennsylvanian age.
No Thoroughfare Canyon at the Colorado National Monument has canyon walls made up of Chinle and Wingate formations and there are some tops of Kayenta and Entrada Sandstones. The trail is on Precambrian rocks.
Bibliography
Taylor, Andrew M. "Colorado National Monument." Guide to the Geology of Colorado. Golden, CO: Cataract Lode Mining, 1999. Print.
"Geologic Formations." Colorado National Monument. 16 May 2011. Web. 16 May 2011. http://www.nps.gove/colm/naturescience/geologicformations.htm.